I wrote support asking why I could no longer log into a client account as a Collaborator. They told me they have disabled this facility:
"Direct login with Collaborator accounts has been disabled, so to login to a store that you manage you can do so directly from your partner account. The change was made to increase the security we can provide for our merchants and will give you a single sign on method for stores you manage going forward."
Was there a memo or email that went out on this that I missed?
I don't know if Staff accounts are still working.
I got further clarification when I asked a few questions:
"Sorry for the confusion about this. We have not disabled Collaborator accounts for stores. However the process to login with a collaborator account has changed. No longer would you go first to the store you want and login, but you would visit your Partner dash and then find the store you manage and login from there.
Collaborator accounts are still requested from the partner who wants to work on a merchants store, then from then on you would access the store to manage it view your partner dashboard rather than the direct login. For your contractors you can create accounts specifically for them with certain permissions see here (just like staff permissions on a merchant's store).
For example your contractor on your account has set permissions to manage stores but perform all actions that the partner account owner can perform. So, for her to access your merchants store, she would log into her partner dashboard and from there see the same options as I sent earlier to login to the store you manage and make changes. This would be the way for her to access the store from now on, and not by attempting to login to the store as an admin there.
I know this initial post is a couple of years old, but I wanted to pop in here and just make it known that there has been a new security feature rolled out for collaborator accounts. Merchants can now choose to set a 4-digit collaborator request code, meaning they will only receive collaborator requests from those who provide this exact code. More information on this new feature can be found over on this thread, and over at the Shopify Help Center.
Victor | Shopify Social Care